Floating causeways have previously been designed and built which provide a downloading ramp at the forward end of the structure, which, when the structure is driven up upon the beach or shore, provide a ramp extending downwardly from the front of the vessel to the beach. Using such ramps, the off-loading of vehicles, personnel and other material is greatly facilitated. However, such structures have met with substantial problems in the past.
For example, the down ramp extending from the forward end of such floating causeways adversely impacts and limits the forward motion of the craft, especially in rough seas. Even in calm seas, the down ramp tends to pull the front end of the structure into the water, limiting the speed of the craft, causing drag, and presenting a sharp angle to the beach or shoreline when the beaching bow is landed. In rough seas, the problems are exacerbated, as the submerged beaching bow causes the waves to flow up and over the front of the structure, potentially causing further vessel control problems, as well as potentially damaging vehicles, supplies and personnel being carried by such causeways.
Other vessels, such as landing craft, have employed powered disembarking platforms which must be raised and lowered either manually or with sophisticated power devices, when the vessel is beached. When such platforms are raised, they can shift the center of gravity of the vessel, creating a top heavy vessel which is less stable. When lowered, they cause the bow to submerge, which greatly decreases speed, and increases the difficulty of making headway and maintaining direction. Again, such problems are exacerbated by rough seas, which greatly increase the drag and buffeting of any watercraft.
For example, the United States Navy employs a Navy Lightered (NL) causeway system, including a proposed Amphibious Cargo Beaching Lighter (ACBL). The ACBL uses modules which are 40 feet long, 24 feet wide, and 8 feet high. The modules are connected together using a rigid pin and guillotine connector. A ramp module is connected to the fore end. However, the ramp module is prone to the problems discussed hereinabove, including submerging, instability and poor beaching interface.
When the watercraft reaches land, inclined surfaces common to beaches makes setting up a disembarking and loading surface more difficult. For cargo, personnel and vehicles to be easily loaded and unloaded, a smooth surface without gaps or drops is required.